"The top 10 contributors gave more than a third, or $68 million of the nearly $202 million reported by the outside spending groups this election," the Center for Public Integrity noted Thursday, in its analysis of Federal Election Commission records.

The superPACs have raised the profile of some wealthy donors who had been relatively anonymous outside of their business fields. On Morning Edition, NPR's Robert Smith took a look at one such donor who would have preferred to remain under the radar.

But The Washington Post reports that publicity-shy donors are finding an alternative: Lots of money is going to politically active nonprofit organizations. As with superPACs, those donations are limited only by the donor's largesse. But unlike with superPACs, donations to these nonprofit organizations are anonymous and normally cannot be tracked back to individual donors.

Nonprofits could play a larger role as the presidential race turns to the general election, the Post reports:

"Nearly all of the independent advertising being aired for the 2012 general-election campaign has come from interest groups that do not disclose their donors, suggesting that much of the political spending over the next six months will come from sources invisible to the public. ...

"Most of the ad spending has come in swing states from conservative groups that criticize President Obama's policies, the data show. Secretive groups have spent tens of millions more targeting congressional races, again mainly in support of Republicans.

"The numbers signal a shift away from superPACs, which are required to disclose their donors to the Federal Election Commission and which have overwhelmed spending in the Republican primary contest. Instead, the battle between Obama and presumptive GOP nominee Mitt Romney appears likely to be dominated by a shadow campaign run by big-spending nonprofits that do not have to identify their financial backers."